We propose to investigate the effects of ganglioside GM1 on the structure of model membranes, the binding of cholera enterotoxin to GM1, and the effects of such binding on membranes incorporating GM1. We will employ physical methods in this research including proton and carbon 13 nuclear magnetic resonance, high sensitivity differential scanning calorimetry and circular dichroism. The knowledge gained from this protein-membrane receptor system will aid in understanding a number of other protein-glycolipid systems including other bacterial entero and neurotoxins, polypeptide hormone action and possibly interferon action.